I want to Integrate Animations with my friend
Once you have defined your rig, you can both save your animations as actions that can be re-used. You can the share the files back with each other and use the append option in the file menu to combine them into one scene if you need.

Actions are blender's way of storing animation sequences for re-use and combining with others, and if you intend to export this to another program like a game engine, are also very useful for managing this. 

You may also find this related question helpful: Reusing Animations for another character?